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Polymerase chain reaction (PCR) is commonly used to amplify and quantify the nucleic acid segments typically using a benchtop thermocycler. To automate, integrate, and miniaturize the PCR process, several strategies have been studied in a microfluidic environment. Among them, continuous-flow-based microfluidic PCR allows fast thermal cycling using minuscule volume, in a minimal reaction time with multiplexing. The objective was to develop a microfluidic device with a soft-lithographically fabricated continuous-flow serpentine microchannel for DNA amplification executed on a separately designed portable, easy-to-use, low-cost, automated, and miniaturized temperature controller platform (TCP). Direct laser writer (DLW) was used for developing a master on glass using a dry-film photoresist (DFR). Further, a PDMS-based microfluidic device, with dimensions 30 (L) × 0.32 mm2 (W) × 35 µm (H), was developed which was bonded on glass using oxygen plasma. The portable device exhibits key features of live data streaming using an IoT platform enabling easy data accessing, monitoring and storage onto the smartphone. The temperature sensitivity of the device was ± 0.5 °C and the maximum achievable temperature was 300 °C. The microfluidic device was placed on TCP. A 20 µL of reaction volume was introduced using an automated syringe pump at various flow rates. As a proof-of-concept, the rat GAPDH gene of the 594-base pair was successfully amplified on the proposed platform which was validated using the gel electrophoresis method. Finally, the results obtained from the proposed device were compared with the conventional thermocycler which showed promising performance and novelty exists in the significant reduction of required amplification time with good device efficiency and low-power consumption.

The introduction of 3D printing technology has revolutionised the manufacturing and electronic product design in the past few years, where it is used to even produce printed circuit boards. Printed electronics is one of the fastest-growing additive manufacturing technologies and is becoming invaluable to various industries. The evolution of several contact and non-contact types of fabrication techniques have been reported in the recent past. Leveraging these technologies, various types of printed electronic components have been realized. One method is inkjet printing technology, which has been widely accepted for printed electronics manufacturing. As 3D printing uses only those materials which are essential to create the product, it eliminates waste production, with a smaller equipment cost and minimizes the number of process steps, resulting in lower manufacturing costs with reduced turnaround time. Various kinds of conductive and non-conductive materials have emerged in the recent past in conjunction with many manufacturing techniques for printed electronics. Herein, we review the most commonly used substrates, electronic printing materials, and the widespread printing techniques employed at the industrial level, giving an overall vision for a better understanding and evaluation of their different features. The technical challenges of several contact and non-contact techniques with corresponding solutions are also presented. Finally, status on advances in the production of various kinds of materials employed in 3D printed electronics and the methods for producing them, shortcomings, technical challenges, applications, benefits, and the future opportunities pertaining to printed electronics are discussed in detail.

Due to the growing popularity of wearable electronics, flexible memory devices are in great demand. The manufacturing method, materials synthesis, and device structure are key obstacles realize the deployable flexible memory devices. Herein, a single-step process of new and highly conductive porous laser-induced graphene (LIG) has been examined which offers higher electrical conductivity, porous structure and flexibility. Also, surface morphology, crystallinity, functional groups in LIG, and oxygen vacancies in MnO 2 nanoparticles have been comprehensively studied for memristor. The, I on / I off ratio of LIG and LIG/MnO 2 was 9.15 and 6.8, respectively. The drop casting of MnO 2 nanoparticles on LIG increases conductivity with oxygen vacancies, improving memristor behaviour of limited I on / I off ratio. The LIG fluid-based memristor with MnO 2 as a metal liquid has outstanding resistance switching capabilities. Moreover, the LIG has showed remarkable performance both substrate and active material for memristor in flexible, wearable, and fluid-based electronics applications. Graphical abstract

Graphite pencil stroked electrodes for paper-based Microfluidic devices are gaining immense attention due to their electrochemical properties, cost efficiency, and ease-of-use. However, their widespread use has been hindered by the challenges associated with their manual fabrication such as non-uniformity in graphite deposition, applied pressure, etc. This work presents the design and development of an automated graphite pencil stroking device for graphite electrode fabrication with high efficiency through a compact, inexpensive and automatic process, with reduced fabrication time and human intervention leading to more uniformity. The motion platform of Graphtec plotter was used to create multiple strokes with the help of the proposed device. Such inexpensive graphite electrodes (less than the US $1) have been observed to be porous in nature, acting as diffusion agents. The automated graphite electrodes were used to study the performance of microfluidic paper fuel cells (MPFCs) with formic acid, oxygen, and sulphuric acid acting as fuel, oxidising agent and electrolyte respectively. From this configuration, the maximum current density and power density were measured to be 1,305.5 µA cm −2 and 135.5 µW cm −2 , respectively at 0.3 V stable OCP at 100 strokes. Overall, the study enumerates the development of an automated pencil stroke device for fabricating graphite electrodes, which can potentially be harnessed in numerous miniaturized paper based applications.

3D-printed portable devices have immense and proven potential to transform the field of electrochemiluminescence (ECL) for diverse biochemical applications. 3D printing (3DP) offers unparalleled ability to build tiny devices in a single step with high accuracy and compatibility, and integrability as per the requirement. In this study, for the first time, a six-well 3D-printed closed bipolar electrochemiluminescence (3DP-CBPE-ECL) device has been successfully fabricated and validated by performing single-step detection of various biochemicals such as glucose and choline. Luminol/H 2 O 2 -based enzymatic reactions were performed with optimized parameters for selective sensing of glucose and choline. The single-step detection of glucose and choline was accomplished for the linear ranges of 0.1 to 10 mM and 0.1 to 5 mM, with a limit of detections (LODs) of 24 µM and 10 µM, respectively. A smartphone was leveraged to execute multiple activities such as powering the ECL device, capturing ECL images, and calculating the ECL intensity of the obtained ECL signal. The feasibility of a six-well 3DP-CBPE-ECL device was tested by sensing glucose and choline simultaneously in a single device at three different concentrations. Furthermore, the concentration of glucose and choline was calculated in real blood serum using the conventional additive (spiking) method, demonstrating the high practicability of the fabricated ECL device and yielding promising findings. Finally, based on the obtained results and other advantages such as low-cost, fast prototyping and requirement of a minimum sample volume, the fabricated six-well 3DP-CBPE-ECL device has shown potential to be used in the field of biochemical applications. Graphical abstract

Vitamin B12 plays a very important role in human body and its deficiency can be detrimental to the production of red blood cells, anemia, memory loss, low immunity to infection, and permanent and severe damage in the nervous system and brain. In the present work, vitamin B12 sensing has been accomplished using two Electrochemiluminescence (ECL) platforms, one with Bipolar Electrode (BPE), while the second one Single Electrode (SE). The electrodes were fabricated on polyimide (PI) substrate by creating optimized Laser-Induced Graphene (LIG). With optimized speed and power of CO2 Laser, non-conducting portion of PI gets converted into conducting zone (electrodes) for ECL imaging. A 3D-printed miniaturized portable system was developed to detect and monitor the ECL signals. Android smartphone was effectively used to provide dual functions such as to drive the DC to DC buck-boost converter and to capture the ECL images. The sensing of vitamin B12 was accomplished in the linear range 0.5–700 nM and 0.5–1000 nM with a limit of detection (LOD) 0.107 nM (R2 = 0.98, n = 3) and 0.094 nM (R2 = 0.977, n = 3), respectively, for BPE and SE-based ECL platforms correspondingly. Therefore, proposed ECL platforms can be selectively used in various domains such as point of care testing (POCT) and biomedical applications.

A Hydrogen fuel cell (HFC) broad range associated with Internet of Things (IoT) technologies that require slightly less and constant electricity made possible by remote climate monitoring connections. Novelty demonstrates a miniature HFC based on carbon cloth electrodes and sealing elements manufactured via 3D printing. Cobalt (II) Oxide (Co 3 O 4 )—reduced Graphene Oxide (rGO) and Platinum (Pt) based nanoparticles are coated over carbon cloth to increase the catalytic activity at the anode and cathode. Hydrogen is produced by using an aluminium foil (Al) that is stored in between the filter paper and through capillary action the sodium hydroxide pellets (NaOH) are applied and reacted with Al foil to produce hydrogen. The single HFC device working surface area of 1 × 1 cm 2 effectively generates an open circuit voltage (OCV) of 1.3 V, a current density of 1.602 mA/cm 2 , and a peak power density of 761 mW/cm 2 . The fuel cell stability performance is monitored for up to 10 h. The power obtained from the HFC is stored in a supercapacitor and used to supply energy to the IoT component. The module includes a built-in sensor that monitors the temperature, pressure, and humidity. The measured data is then transmitted to a smartphone via Bluetooth.

Controlled, stable and uniform temperature environment with quick response are crucial needs for many lab-on-chip (LOC) applications requiring thermal management. Laser Induced Graphene (LIG) heater is one such mechanism capable of maintaining a wide range of steady state temperature. LIG heaters are thin, flexible, and inexpensive and can be fabricated easily in different geometric configurations. In this perspective, herein, the electro-thermal performance of the LIG heater has been examined for different laser power values and scanning speeds. The experimented laser ablated patterns exhibited varying electrical conductivity corresponding to different combinations of power and speed of the laser. The conductivity of the pattern can be tailored by tuning the parameters which exhibit, a wide range of temperatures making them suitable for diverse lab-on-chip applications. A maximum temperature of 589 °C was observed for a combination of 15% laser power and 5.5% scanning speed. A LOC platform was realized by integrating the developed LIG heaters with a droplet-based microfluidic device. The performance of this LOC platform was analyzed for effective use of LIG heaters to synthesize Gold nanoparticles (GNP). Finally, the functionality of the synthesized GNPs was validated by utilizing them as catalyst in enzymatic glucose biofuel cell and in electrochemical applications.

Antimicrobial resistance (AMR) is a global health threat, progressively emerging as a significant public health issue. Therefore, an antibiotic susceptibility study is a powerful method for combating antimicrobial resistance. Antibiotic susceptibility study collectively helps in evaluating both genotypic and phenotypic resistance. However, current traditional antibiotic susceptibility study methods are time-consuming, laborious, and expensive. Hence, there is a pressing need to develop simple, rapid, miniature, and affordable devices to prevent antimicrobial resistance. Herein, a miniaturized, user-friendly device for the electrochemical antibiotic susceptibility study of Escherichia coli (E. coli) has been developed. In contrast to the traditional methods, the designed device has the rapid sensing ability to screen different antibiotics simultaneously, reducing the overall time of diagnosis. Screen-printed electrodes with integrated miniaturized reservoirs with a thermostat were developed. The designed device proffers simultaneous incubator-free culturing and detects antibiotic susceptibility within 6 h, seven times faster than the conventional method. Four antibiotics, namely amoxicillin–clavulanic acid, ciprofloxacin, ofloxacin, and cefpodoxime, were tested against E. coli. Tap water and synthetic urine samples were also tested for antibiotic susceptibility. The results show that the device could be used for antibiotic resistance susceptibility testing against E. coli with four antibiotics within six hours. The developed rapid, low-cost, user-friendly device will aid in antibiotic screening applications, enable the patient to receive the appropriate treatment, and help to lower the risk of anti-microbial resistance.

This paper demonstrates screen-printing technique, Glass Screen printed (GSP) on glass layer with Graphene Quantum Dots (GQDs) via drop casting approach to manufacture electrodes for Miniaturized Microbial Fuel Cells (MMFCs). MMFCs are viable options to sustainably operate low-power devices such as sensors, implantable medical devices, etc. However, the technology is still not fully mature for practical applications due to limitations of output power. Materials and design improvements are required for decreasing internal resistance for better electron transfer and improving overall performance. In this work the electrodes manufactured by GSP technique, and anode modified by GQD was tested in MMFC using RO wastewater. It was found that the GQDs increased the surface area to improve electron transfer kinetics at the anode. As a result, GQDs-based GSPEs showed 7.4 times higher power output 332 nW/cm 2 compared to its unaltered electrode which displayed a power output of 44.8 nW/cm 2 . Electrodes made by GSP technique are more durable and less susceptible to biofouling and corrosion compared to conventional methods. The modified anodes further showed sustained output for long term operation.